Reversible stepping mechanisms



Oct. 14, 1969 K. J. YLINEN 3,472,087

REVERSIBLE STEPPING MECHANISMS Filed March 22, 1968 Fig. 1

United States Patent O 3,472,087 REVERSIBLE STEPPING MECHANISMS Klaus Johannes Ylinen, Frejgatan 13, Stockholm, Sweden Filed Mar. 22, 1968, Ser. No. 715,228 Claims priority, application Sweden, Mar. 23, 1967, 4,116/ 67 Int. Cl. F16h 27/02 U.S. Cl. 74--143 3 Claims ABSTRACT F THE DISCLOSURE A reversible stepping mechanism comprises a ratchet wheel having teeth of substantially isosceles triangle shape, and two solenoid-actuated drive pawls, one on either side of the diametral plane of the ratchet wheel, for selectively driving the ratchet wheel stepwise in either direction. The pawls have tooth-contacting portions and are mounted resiliently in such a manner that they are bent out of the way of the teeth upon disengagement of the pawl from the teeth.

A stepping mechanism comprises a ratchet wheel whose teeth are engaged one by one by a pawl that has a portion which is resiliently mounted to be deflected by the next tooth upon withdrawal of the pawl from the ratchet wheel.

The present invention relates to stepping mechanisms, more particularly of the reversible type in which two pawls disposed on opposite sides of the diametral plane of a ratchet wheel selectively drive the wheel stepwise in either direction.

It is an object of the present invention to provide such a mechanism in which there will be no undesirable interference between the ratchet teeth and the pawls.

Another object of the invention is to provide such a mechanism which will be relatively simple and inexpensive to manufacture, easy to operate, maintain and repair, and rugged and durable in use.

yOther objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawing, in which:

FIGURE 1 is a view of a stepping mechanism according to the present invention;

FIGURE 2 is a fragmentary View of a portion of the structure of FIG. l taken perpendicular to the plane of symmetry of FIG. 1;

FIGURE 3 is an enlarged fragmentary view showing the relationship of one pawl to the ratchet wheel at the middle of the stepping motion; and

FIGURE 4 is a view similar to FIG. 3 but showing the relationship of a pawl to the ratchet wheel at the end of a stepping motion.

Referring now to the drawing in greater detail, a bushing 1 is secured in a holding plate 2, and in the bushing 1 is rotatably mounted a shaft 3, to the end of which shaft is attached a ratchet wheel 4. The wheel 4 is provided along its circumference with a series of teeth 5 of substantially isosceles triangle shape. On each side of the ratchet wheel is mounted a solenoid coil 6 with an iron core 7. The coils are secured to the plate 2, for example by means of a threaded journal arranged at one end of the core 7 and a nut screwed onto said journal. The journal extends through a hole in a tab 2a bent perpendicularly from the base plane of the plate 2.

A yoke portion 8 is clamped with one leg between the solenoid coil 6 and the tab 2a. It has an intermediate portion 9 which is deilected perpendicularly from the leg,

ICC

directed along the solenoid axis and located adjacent to the solenoid coil. The yoke portion 8 is completed with an armature 10 which is rockingly mounted at the end 0f the intermediate portion 9 opposite to said leg.

A pawl 11 is mounted on the armature 10. To the outer end of the pawl according to FIG. 1, which end extends beyond the corresponding end of the armature 10 and is slightly bent downwards (in FIG. 1), one end of a tension spring 12 is fastened, the other end of which is fastened to the intermediate portion 9. Owing to the traction of the spring 12, the end of the pawl 11 facing the ratchet wheel 4 is kept out of engagement with the teeth 5 of the ratchet wheel 4, as shown in FIG. l, when the solenoid is deenergized. The last-mentioned end 13 of the pawl 11 is bent to U-shape, and between the legs of this U-shaped end is arranged one leg 14 of an Lshaped member 14, 15 which is rockingly mounted in a slot 16 close to the bottom or bend of the U-shaped end 13. The other leg 15 extends through the slot 16, and at the outer end of said leg is fastened one end of a tension spring 17, the other end of which is fastened to the base portion of the pawl 11. Due to the `action of spring 17, the L-shaped portion is resiliently supported in the position shown in FIG. 1 when the free outer end of its leg 14 is not subjected to external force. The member 14, 15 is thus rockingly mounted in the slot 16 at the transition between the legs 14, 15. A leaf spring 18 bears against the ratchet wheel 4 in the manner shown in order to prevent motion of the wheel 4 at the nonoperative position shown in FIG. 1. A stop pin 19 limits the motion of the pawl 11 in the direction away from the iron core 7.

The step mechanism operates as follows:

A current impulse to the solenoid coil 6 effects the attraction of the armature 10 by the iron core 7. The pawl 11 moves together with the armature in the direction of the arrow 21 (FIG. 3), so that the outer end of the leg 14 is applied close to the tip of a tooth 5 and slides along the tooth tlank 20 (see FIG. 3) while turning the ratchet wheel 4 in the direction of the arrow 22. In the position of the pawl 11 and ratchet wheel 4 shown in FIG. 3, the end of the leg 14 has reached the bottom of the tooth gap and turned said wheel through an angle 23 corresponding to half a tooth division. The motion of the pawl 11 and ratchet wheel 4 continues to the position shown in FIG. 4 in which the ratchet wheel was turned through the angle 24 corresponding to an entire tooth division. Thereby the leg 14 lies llat along the opposite tooth flank 25 of the next following tooth. The armature 10 is at this point entirely attracted into abutment against the iron core 7. Upon the cessation of the current impulse to the solenoid, the armature 10 is disengaged and, by the action of the spring 12, is pulled away together with the pawl 11 from the ratchet wheel 4 to the position shown in FIG. l. The leg 14 thereby returns from the position shown in FIG. 4, where it is disposed parallel to the right-hand leg of the U-shaped end 13, to the position shown in FIG. 3 where it lies flat along the left-hand leg of the end 13. The mechanism is then ready to carry out an additional stepping motion, upon a new current impulse from the solenoid.

The description of the function has been restricted to the right-hand part of the mechanism according to FIG. l, but it is obvious that the left-hand part of the mechanism operates in a corresponding way for stepping the ratchet wheel in the opposite direction. It further is obvious that at least the pawls 11 are arranged symmetrically in relation to a vertical diametrical plane through the ratchet wheel 4 in FIG. 1, and that the teeth 5 are of isosceles triangle shape for obtaining steps of equal length when stepping in clockwise and counterclockwise directions.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the invention have been achieved.

Although the present invention has been described and illustrated in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention as those skilled in this art will readily understand. For example, the drive of the pawls, instead of being electromagnetic, may be purely mechanical. These and other modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

Having described my invention, I claim:

1. In a stepping mechanism comprising a ratchet wheel mounted for rotation about its axis and having ratchet teeth thereon, a drive pawl engageable with the ratchet teeth one by one to rotate the ratchet wheel stepwise, and means for moving the pawl into and out of engagement with the ratchet teeth; the improvement comprising means resiliently supporting that portion of the pawl which contacts a ratchet tooth so that said pawl portion will be deliected by the next ratchet tooth during movement of the pawl away from the ratchet wheel, said pawl having a U-shaped end portion which opens toward the ratchet wheel, said pawl portion being rockable between the legs of said U-shaped end portion.

2. Mechanism as claimed in claim 1, and a spring acting against said pawl portion to urge said pawl portion endwise outwardly of said pawl.

3. Mechanism as claimed in claim 2, said pawl having a base portion on which said U-shaped end portion is disposed, said resiliently supported pawl portion being in the form of an L-shaped member having one leg disposed between the legs of said U-shaped end portion and the other leg extending through a slot close to the bottom of the U-shaped end portion, and a spring in tension between said other leg and said base portion of the pawl.

References Cited UNITED STATES PATENTS 2,377,583 6/1945 Smith 74-142 2,150,680 3/1939 Fuller 74-142 2,990,723 7/ 1961 Holpuch 74-142 2,994,227 8/ 1961 Lips et al 74--142 FRED C. MATTERN, J R., Primary Examiner W. S. RATLIFF, JR., Assistant Examiner 

